A supplanter takes over or takes the place of someone else, usually on purpose. If usurping thrones is your thing, then maybe you have a future as a supplanter.
A supplanter takes the place of someone or something that was there first. For example, a new big-name donut shop may become a supplanter if it hurts or ruins the business of the local Mom and Pop donut shop. Supplanter often refers to governments and rulers of countries, and it comes from the verb supplant, which evolved from the Latin supplantare, meaning "to trip up or to overthrow."